DE69318023T2 - TARGET AND ALIGNMENT SYSTEM FOR A GROUND ARMOR DEVICE - Google Patents

Description

STATE OF THE ART

The present invention relates generally to aim and aiming systems for ground weapon equipment, and more particularly to a system of the type described which utilizes a north finding system. In particular, the present invention relates to a system which provides the operator with the aiming angles of a weapon relative to north and the local horizontal and relative to a target.

Prior art systems for the purposes described include a gyrocompass device that uses a conventional two-axis rotating wheel gyro to find the angle of the weapon relative to north. The angle is then optically transferred to a fixed standard called a sighting circle. The device is removed from the weapon prior to firing. Any corrections for angle errors caused by firing are then eliminated by optically realigning the weapon to the sighting circle.

Gyrocompass devices are known which have a stabilized reference arrangement. Such an arrangement contains a precision gyro which is held in the horizontal position by separating the gyro from the weapon on a stabilized platform. This technique is inevitably cumbersome and expensive since it requires a mechanism with at least three gyros, two level measuring devices and three gimbals.

Strap-down ring laser gyro arrays are also known. This technology is also more complicated and expensive than one would wish, since it must contain three ring laser gyros and three accelerometers, as the expert will appreciate.

The above-mentioned prior art arrangements present several problems that must be solved. For example, the weapon must be leveled to within 0.25 degrees of horizontal for the gyrocompass to function. Due to mass imbalance error terms and characteristics, rotating wheel gyros have deteriorated accuracies when operating as gyrocompasses on inclines. Even when leveled, such arrangements for long-range projectiles have only marginal accuracies. A typical accuracy value is five thousandths of an inch (one sigma).

Furthermore, rotating wheel systems cannot be permanently attached to the weapon during transport or weapon firing because the vibration and shock that occurs reduces the reliability of the system. As a result, these systems only maintain the initial angle of aim of the weapon and are not useful for providing continuous aiming data during aiming or after the weapon has been fired. Also, assembly and disassembly of these systems is inefficient at best and even dangerous during weapon firing conditions.

Also, the reliance on the above-mentioned optical transmission of the setting angle to a directional circle prevents the application of current optical techniques when obscuring conditions such as rain, snow, smoke or other environmental abnormalities occur. Also, optical transmission methods are time-consuming and subject to human error.

Techniques using three gyroscopes require that the gyroscopes be accurate enough to be used for the intended purposes and are therefore too expensive for practical application.

The present invention overcomes these problems and has several other significant advantages. For example, with the arrangement to be described here, the gyrocompass function can be performed for any weapon elevation up to 25 degrees from the horizontal, since the gyro used, which is preferably a ring laser gyro or a gyro of some other type that has mass imbalance error characteristics is unaffected, is insensitive to inclination. Time to level the weapon for gyrocompassing purposes is not required, and after gyrocompassing the system continues to measure the weapon angles for each weapon attitude. Furthermore, the accuracy of the system described here has been found to be less than or equal to one thousandth of an inch under military environmental conditions.

The system can also be permanently attached to the weapon. It is inherently robust in design and tolerant of shock and vibration. Therefore, updates to the weapon angles are continuously provided as the weapon is slewed to the target direction.

A special feature of the invention is that it contains its own indicators for indicating aiming angles, making it useful in a variety of otherwise disturbing environmental conditions. Furthermore, the system can be used to realign the weapon immediately after firing, without any auxiliary equipment.

Furthermore, the present invention enables the performance requirements to be met by using a single gyro and two accelerometers as sensors. Compared to systems known in the art today for the purposes described, the design is therefore more economical.

Reference is now made to commonly assigned U.S. Patent 5,060,392, issued to Mark S. Grasso on October 29, 1991. The patent relates to a gyrocompass (north finding) system intended for a land-based facility requiring north reference information, and includes a gyrocompass implementation that allows the use of high quality inertial sensors while achieving the desired goal of modest cost. The north finding system is designed to provide high accuracy with fast response time over a wide temperature range without the aid of heaters and other auxiliary devices. The arrangement is specifically designed to tolerate transient and/or base oscillation motion without additional response time or degradation of gyrocompass accuracy. The measurement axis of a gyro used in the system is inclined so that it can measure a gimbal rotation component, thus eliminating the need for an independent measurement of the relative gimbal angle. The required absolute position between the gimbal and the system housing is achieved by an appropriate stop arrangement, which is an easier task than measuring the relative gimbal angle as mentioned above.

Thus, the invention of US Patent 5,060,392 relates only to north finding and does not relate to an adjustment system for a ground-based weapon system such as the present invention.

An embodiment of the present invention provides a north finding means of the type in which an inertial platform carries measuring instruments including a single gyro of the type without a rotating mass so as to be insensitive to mass imbalance effects, a measuring axis of said gyro being positioned on the horizontal or slightly oblique thereto for gyrocompass purposes, and control means comprising:

a targeting and adjustment system for ground weapons equipment;

the gyroscope being attached to a rotating part of a weapon adjustment structure of the ground weapon equipment so that the measuring axis rotates therewith when the said weapon structure is adjusted, the gyroscope causing the measurement of the rotational speed of the earth during north-seeking and the slewing speed of the weapon structure after north-seeking;

wherein said north finding means is effective to continuously measure the azimuth and elevation angles of the adjusted weapon structure and to provide corresponding signals;

a display means which is connected to the control means in an output mode and is connected to the operator to apply signals corresponding to the azimuth and elevation angles of a target and signals corresponding to the slew rate of the weapon structure to said control means, the control means being responsive to all said signals to drive the inertial platform to align the one gyroscopic axis with the rotating weapon structure and to provide output signals; and

the display means connected in an input mode to the control means and responsive to the output signals provided thereby for displaying at least weapon azimuth, elevation and wheelbase angles in real time, aiming and elevation signals in real time and the differences between said weapon and aiming signals in real time and for indicating the direction in which the weapon structure must be slewed to point at the target and when the weapon structure is properly aimed.

Another embodiment of the invention provides a method for aiming and adjusting a weapon structure of a ground weapon system with supporting measuring devices including a single gyroscope of the type without rotating mass to be insensitive to mass imbalance effects on an inertial platform, said gyroscope having a single measuring axis, comprising:

Attaching a north-seeking system including the inertial platform to a rotating part of the weapon structure so that the north-seeking system rotates with it;

Entering north and east distances and azimuth and elevation angles of a target into the north finder system;

Aligning the individual measuring axis of the gyro to the weapon structure;

Measuring the output of the inertial platform;

Using the measured output of the inertial platform to determine weapon approach angles and weapon aiming angles;

Using the specific angles to display at least real-time weapon azimuth, elevation and wheelbase angle information, real-time target azimuth and elevation angle information, and the difference between the weapon and target angle information in real-time and for displaying information regarding the direction in which the weapon must be slewed to point at the target and when the weapon is properly aimed; and

Combining the displayed information with the measured gyro output to redetermine weapon approach angles and weapon aiming angles.

The present invention relates to a pointing and setting system for a ground weapon system including a north finding system and an indicator assembly. The north finding system is attached to the rotating part of the weapon structure so that it rotates with a pointed weapon. The north finding system contains the inertial components, electronics and the computer used to find and continuously measure the azimuth and inclination angles of the pointed weapon. The north finding system according to US-A-5060392 is only applicable to measuring the initial setting angles. The present invention extends the north finding system as required to perform the pointing function after the gyrocompass function has been completed.

A gyro in the north finding system is offset from the horizontal plane at an angle large enough to ensure that (1) the gyro measuring axis can measure a horizontal component at the rotational speed of the earth to perform the gyrocompass function, and (2) the gyro measuring axis can measure a vertical rotational component during the azimuth tracking mode of the device. This is achievable by offsetting the system cradle frame, the platform within the cradle frame, and the gyro within the platform.

The display arrangement contains a keyboard through which control personnel can command the north-seeking system to carry out its functions and enter data required for the north-seeking system calculations. The arrangement displays real-time weapon azimuth, elevation, and wheelbase orientations, real-time target azimuth and elevation orientations, real-time difference between target and weapon angles, and other applicable data needed to perform a specific mission.

The display assembly further includes indicator means for showing a gunner the direction in which the weapon must be swung to point at the target and when the weapon is properly aimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a block diagram showing the invention in general,

Figure 2 is a functional block diagram of the invention,

Figure 3 is a flow chart illustrating the sequence of operation of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figure 1, a north-finding system is designated by the numeral 1 and includes an inertial platform 2 and a display unit 4. An electronics unit 8 is connected to the inertial platform 2 and a central processing unit (CPU) 10 is connected to the electronics unit 8. The central processing unit 10 is connected to the display unit 4 in an input/output configuration. The north-finding system 1 with the inertial platform 2, electronics unit 8 and CPU 10 is attached by suitable means 11 to the rotating part of a weapon adjustment structure 13 of the ground weapon equipment 15 so that the north-finding system rotates with the ground weapon equipment.

Next, components 2, 4, 8 and 10 and the detailed interaction between them are described with reference to Figure 2, wherein corresponding elements to those in Figure 1 have corresponding numerical designations.

Referring now to Figure 2, the Inertial platform 2 the several inertial measuring devices of the north finding system 1, which are mounted on a pivot point 6. The pivot point 6 is used to realize gyrocompass index positions.

The electronics unit 8 contains gyro assist circuits and pivot index circuits. The electronics unit 8 and CPU 10 provide the necessary control, compensation, calculation and interface functions for the north finding system 1 and the display unit 4.

The pivot 6, supported for rotation by bearings 5 in a housing 7, provides the ability to index the multiple inertial sensors to the various positions required for the gyrocompass function. The pivot 6 carries a torque generator 12 to provide drive capability, a resolver 14 to provide an angle reading, and the pivot latch 16 which is energized to allow rotation or indexing of the pivot 6, but is otherwise locked to strap down the platform module. Those skilled in the art will recognize that the resolver 14 can be replaced by a suitable optical encoder.

Gyrocompass data is always collected with the pivot 6 locked, i.e., the latch 16 de-energized. A gyro 18, which is a type of gyro insensitive to force imbalance effects and is therefore preferably a ring laser gyro, measures the rotational rate of the earth during the north-seeking mode of the system and provides a rim rotational rate signal which is a frequency modulated analog signal having a frequency proportional to the rotational rate. The ring laser gyro 18 measures the weapon traverse rates after north-seeking by attaching the north-seeking system 1 to the rotating portion of the weapon structure 13 as described with reference to Figure 1.

The ring laser gyro 18 provides an edge rotation speed signal which is a frequency modulated Analog signal having a frequency proportional to the rotational speed. This signal is conditioned, digitized and accumulated for software processing via the signal conditioner 20, digitizer 22 and accumulator 24. The ring laser gyro 18 provides a laser beam intensity signal and phase modulated instantaneous amplitude signals. These signals are processed via the path length control means 26 and phase modulation control means 28 which are controlled by the CPU 10 via DA converters 29 and 31 respectively. The ring laser gyro 18 is powered by a high voltage power supply 19 via a current regulator 21.

X-accelerometers 30 and Y-accelerometers 32 are used to measure the inclination of the gyro 18 and to measure the basic motion of the primary equipment, i.e., the weapon 15 in the gyrocompass implementation. The analog outputs provided by the accelerometers 30 and 32 are analog DC voltages that are multiplexed through a multiplexer (MUX) 34 and digitized through an A-D converter 36 and then applied to the CPU 10. In another embodiment of the invention, these voltages would be processed by voltage-to-frequency converters and then applied to the CPU 10, as will be appreciated by those skilled in the art.

As already mentioned, the electronics 8 provide the control of the pivot point 6. A locking drive 38 is activated by the CPU 10 to release the pivot point 6 for rotation and is deactivated by the CPU to lock the pivot point again.

A torquer drive 40 energizes the torquer 12 in response to torquer commands provided by the CPU 10 via a D/A converter 42 to the index pivot 6. Resolver information, i.e., coarse and fine, is digitized by a resolver-to-digital (R/D) converter 44 to provide the required pivot positioning and reference adjustment of the plurality of inertial measuring devices to the platform module mounting shoes (not otherwise shown).

To the extent described so far, the Nordauchsystem 1 corresponds to that disclosed in US-A-4,945,647. Only that part of the said description which is necessary for a full understanding of the invention has been included here. The full description and the associated analytical discussion are contained in the above-mentioned US-A-4,945,647.

The CPU 10 is of the type that uses a conventional chip and a number of peripherals. The memory consists of an EPROM 46, a NOVRAM 48 and a RAM 50. A microprocessor 51 is connected between the EPROM 46 and RAM 50. A NOVRAM calibration means is used to store inertial measurement device and alignment calibration constants and to allow these parameters to be updated as necessary. The NOVRAM 48 is controlled by the control logic 49.

A universal asynchronous receiver/transmitter (UART) 52 is connected to the CPU memory via the microprocessor 51 and is connected via input/output lines to a control and display unit 58 and a gunner display unit 60, both of which are contained in the display unit 4. The control and display unit (CDU) 58 contains a keyboard used to command the north finder system to perform its functions and to enter data required for north finder calculations. The CDU 58 displays real-time weapon azimuth, elevation and wheelbase, real-time target azimuth and elevation, the difference between the target and weapon angles in real-time, and other pertinent data required to perform a particular mission. In this respect, the CDU 58 is operated by a weapons command officer or equivalent personnel.

The gunner display unit (GDU) 60 is a display type device. One device that can be used with the present invention includes, for example, a vertical row illuminated arrows, a horizontal row of illuminated arrows, and an illuminated indicator at the intersection of the horizontal and vertical rows. The arrows show a gunner the direction in which to turn the gun to point at the target. The number of arrows indicates the amount of movement required to aim at the target. As the gun approaches the aiming angle, the arrows furthest from the center are extinguished. When all the arrows are extinguished and the center indicator is illuminated, the gunner is confident that the gun is correctly aimed.

The electronics unit 8 further contains a DC converter 54 with an electromagnetic interference (EMI) filter to ensure electromagnetic compatibility and also contains power conversion electronics 56 to generate the required sinusoidal current to the resolver 14. In this regard, reference is again made to the above-mentioned US patent 4,945,647.

Reference is now made to Figure 3 which illustrates the course of operation of the invention. Thus, when the system of the invention is turned on, north and east ranges and target azimuth and elevation data are entered into the CPU 10 via the operator operated CDU 58. The CPU 10 then causes the inertial platform 2 to rotate to align the measurement axis of the gyro 18 (Figure 2) with the weapon 15 (Figure 1). The inertial platform 2 is locked in place by the CPU 10 (Figure 2) which controls the locking drive 38 and the pivot latch 16 (Figure 2).

The outputs of the gyro 18 and the accelerometers 30 and 32 (Figure 2) are measured and used by the CPU 10 to determine new weapon attitude angles and new weapon aiming angles.

The determined angle information is transmitted to the CDU 58 (Figure 2) for display thereon and is transmitted to the GDU 60 (Figure 2) for providing a display to gunner personnel.

CDU 58 and GDU 60 transfer expenditures that are the measured outputs of the gyros and accelerometers are combined to recalculate the attitude angles and weapon-aiming angles.

It can now be seen that a system has been described which accommodates modern warfare logistics which require highly maneuverable ground forces. The system enables large mobile weapons to be quickly and accurately aligned to engage targets after deployment at a new location. The azimuth elevation and wheelbase of a weapon can be determined within a relatively short time after system activation at the location. The system includes its own display for indicating the angle of attack of the weapon. Means are provided for entering inputs into the system corresponding to desired aiming angles. The system then indicates the direction and amount of rotation of the weapon to align with the target.

As the weapon is slewed toward the target, two separate displays, i.e. the CDU and the GDU displays, provide continuous updates of the relationship of the weapon-target angles.

When the target is aligned within a specified accuracy, an indicator is provided to alert the operator that no further adjustment is necessary. In this regard, it should be noted that it is to be expected that the weapon may move away from the target due to the firing recoil. This angular movement is measured by the system and can be used to quickly re-acquire the target in the same way as for the initial aiming.

Thus, an independent automatic system is disclosed which is used to determine azimuth and elevation data for a weapon setting system. North and attitude reference values are provided for the setting system and the reference values are maintained during operation of the weapon. Information is provided to the operator indicating angular errors of the desired setting direction and to the Operators are provided with indicators to indicate when the weapon is properly aligned.

With the above description of the invention in mind, reference is made to the appended claims for a definition of the scope of the invention.

Claims (2)

1. North finding means (1) of the type in which an inertial platform (2) carries measuring instruments including a single gyro (18) of the type without rotating mass so as to be insensitive to mass imbalance effects, an input axis of said gyro (18) being positioned on the horizontal or, for gyrocompass purposes, slightly obliquely therefrom, and control means (8, 10) comprising: an aiming and adjustment system (13) for a ground weapon equipment (15); the gyroscope (18) being attached to a rotating part (above 11) of a weapon setting structure of the ground weapon equipment (15) such that the measuring axis rotates therewith when said weapon structure is set, the gyroscope (18) causing the measurement of the rotation speed of the earth during north-seeking and the slewing speed of the weapon structure after north-seeking; wherein said north finding means (1) is effective for continuously measuring the azimuth and elevation angles of the adjusted weapon structure and providing corresponding signals; a display means (4) connected to the control means in an output mode and actuated by the operator in the output mode to apply signals corresponding to the azimuth and elevation angles of a target and signals corresponding to the slewing speed of the weapon structure (13) to said control means (8, 10), the control means (8, 10) being responsive to all of said signals to control the inertial platform (1) to align the one gyroscopic measuring axis with the rotating weapon structure (13) and to provide output signals; and the display means (4) connected in an input mode to the control means (8, 10) and responsive to the output signals provided thereby to display at least weapon azimuth, elevation and wheelbase angles in real time, target and elevation signals in Real time and to display the differences between said weapon and target signals in real time and to indicate the direction in which the weapon structure (13) must be swiveled to point at the target and when the weapon structure (13) is correctly aimed. 2. A method of aiming and adjusting a weapon structure of a ground weapon system with supporting measuring devices including a single gyroscope of the type without a rotating mass to be insensitive to mass imbalance effects on an inertial platform, said gyroscope having a single measuring axis, comprising: Attaching a north-seeking system including the inertial platform to a rotating part of the weapon structure so that the north-seeking system rotates with it: Entering north and east deviations and azimuth and elevation angles of a target into the north finder system; Aligning the individual measuring axis of the gyro to the weapon structure; Measuring the output of the inertial platform; Using the measured output of the inertial platform to determine weapon approach angles and weapon aiming angles; Using the determined angles to display at least real-time weapon azimuth, elevation and wheelbase angle information, real-time target azimuth and elevation angle information, and the difference between the weapon and target angle information in real-time and to display information regarding the direction in which the weapon must be slewed to point at the target and when the weapon is properly aimed; and Combining the displayed information with the measured gyro output to redetermine weapon approach angles and weapon aiming angles.